Combined capacitor-inductor reactor device having transformer characteristics

ABSTRACT

A combined capacitor-inductor reactor formed by spaced-apart layers of insulation and conductive foil rolled together around a core member to form a combined capacitor-inductor reactor. By connecting the input supply terminals to two different points on the same conductive foil and deriving the output from across a portion of the second foil which is coextensive with the part of the first coil intermediate the input terminals, the structure will exhibit capacitor connected transformer characteristics suitable for use as a fluorescent lamp starting and ballast circuit.

' United States Patent Grahame 1151 3,704,390 1451 Nov. 28, 1972 1COMBINED CAPACITOR-INDUCTOR REACTOR DEVICE HAVING TRANSFORIVIER-CHARACTERISTICS [72] Inventor: Frederick W. Grahame, 22 Grant Avenue,Glens Falls, NY. 12801- [22] Filed: Jan. 26, 1972 [21] Appl. No.:221,113

Related US. Application Data I [63] Continuation of Ser. No. 40,272, May25,

.1970, abandoned.

[52] US. Cl. 315/276, 315/282, 336/69, 336/90, 336/94, 336/100 [51] Int.Cl ..H01f 15/14, l -l0lf 27/02 [58] Field of Search ..336/96, 100,69,70, 90, 92, 336/94, 150, 165; 315/276, 282

[56] References Cited UNITED STATES PATENTS 3,078,411 2/1963 Book..336/150 X 3,210,648 10/1965 Lockie ..336/70 X 2,521,513 9/1950 Gray..336/165 X 3,456,221 7/1969. Martin et al. "1336/69 7 366,544' 7/1887Westinghouse, Jr.....336/96 x 3,210,706 10/1965 Book ..336/69 x3,210,705 10/1965 Lockie ..336/69 x 3,210,703 10/1965 Lockie ..336/69 x3,210,704 10/1965 Book ..336/69 x 3,077,946 2/1963 Wilkins ..336/100 x3,161,843 12/1964 Hodges et a1 ..336/96 Primary Examiner-Thomas J. KozmaAttorney-James J Lichiello 1571 3 ABSTRACT A combined capacitor-inductorreactor formed by spaced-apart layers of insulation and conductive foilrolled together around a core member to form a combinedcapacitor-inductor reactor. By connecting the input supply terminals totwo different points on the same conductive foil and deriving the outputfrom across a portion of the second foil which is coextensive with thepart of the first 'coil intermediate the input terminals, the structurewill exhibit capacitor connected transformer characteristics suitablefor use as a fluorescent lamp starting and ballast circuit.

6 Claims, 6 Drawing Figures PATENTEU NOV 28 I972 INPUT FIG.6.

INVENTOR: FREDERICK W. GRAHAME,

s ATTORNEY.

COMBINED CAPACITOR-INDUCTOR REACTOR DEVICE HAVING TRANSFORMERCHARACTERISTICS This is a continuation of application Ser. No. 40,272,filed May 25, 1970, now abandoned.

BACKGROUND OF THE INVENTION duction Apparatus, issued Sept. 5, 1950,discloses a number of different known constructions for combinedcapacitor-inductor reactor devices. These known devices, while suitablefor a number of electrical applications, have not proven entirelysatisfactory for certain uses because of their operatingcharacteristics. The present invention makes available an improved,combined capacitor-inductor reactor device having capacitor connectedtransformer vcharacteristics, and is ideally suited for use as astarting and ballast circuit for fluorescent lamps.

SUMMARY OF THE INVENTION It is therefore a primary object of theinvention to provide a new and improved combined capacitor-inductorreactor structure.

Another object of the invention is to provide such a structure whichexhibits capacitor connected transformer characteristics and is suitablefor use as a starting and ballast circuit for fluorescent lamps.

A still further object of the invention is the provision of a combinedcapacitor-inductor reactor structure having improved startingcharacteristics as well as improved sound deadening and heatdistribution properties.

In practicing the invention a combined capacitor-inductor reactor deviceis provided which is of the type including at least first and second,spaced-apart, tapelike conductive foils having intervening layers ofelectrical insulation rolled together to form a combinedcapacitor-inductor reactor. The improvement comprises first terminalmeans connected to a point on one of the conducting foils and secondterminal means connected to a different point on the same conductivefoil with third and fourth terminal means being connected across atleast a portion of the second conductive foil that is coextensive withthe portion of the first conductive foil intermediate the first. andsecond terminal points. The point of connection of the first terminalmeans preferably is at one end of the first conductive foil with thesecond terminal means being connected at some point intermediate thelength of the first conductive foil. The third and fourth terminal meansare connected preferably across the respective ends of the secondconductive foil in a manner such that the capacitor-inductor reactordevice operates as a transformer having a fixed capacitor seriallyconnected with its secondary winding. The turns ratio of thistransformer is determined by the relative lengths of the first andsecond conductive foils intermediate the first and second terminal meansand the third and fourth terminal means, respectively.

Preferably, the combined capacitor-inductor reactor device includes amagnetically permeable core member which is surrounded by the rolledturns of the tapelike conductive foils and intervening layers ofelectrical insulation. This entire structure including the core memberthen preferably is enclosed in a suitable liquid tight metal caseproviding electrical insulated terminal connections to the respectivefirst through fourth terminal means, and the rolled conductive foils andinterclosed in a second outer housing providing access to the insulatedterminal connections and having the space intermediate the second outerhousing and the metal case filled with a suitable ballast compoundsuchas sand-loaded asphalt for improved sound deadening and heatdistribution. In preferred embodiments of the invention, the first andfourth terminals may in fact comprise a single, common terminal pointthat is suitable for grounding.

. BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and many ofthe attendant advantages of this invention will be appreciated morereadily as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings, wherein like parts in each of the several figuresare identified by the same reference character, and wherein:

FIG. 1 is a perspective view of a partially disassembled coil oftape-like, conductive foil having intervening layer electricalinsulation and rolled together to form a combined capacitor-inductorreactor structure.

FIG. 2 is a schematic illustration of the structure shown in FIG. 1 ifit were unrolled into a straight line structure, and depicts the mannerin which the structure derives its capacitive characteristics.

FIG. 3 is a perspective view of the structure shown in FIG. I mounted ona suitable core member of magnetically permeable material.

FIG. 4 is a schematic physical illustration of the manner of connectionof the input supply terminals and load deriving output terminals to thecap-reactor structure of FIG. 3.

FIG. 5 is an equivalent circuit diagram of the capreactor structureconnected as shown in FIG. 4.

FIG. 6 is a partial sectional view of a complete, combinedcapacitor-inductor reactor structure including an improved liquid tight,sound proof, outer supporting casing constructed in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view ofa combined capacitorinductor reactor (hereafter referred to as acap-reactor) formed by rolling together two tape-like sheets ofconductive foil 11 and 12 with the conductive foils l1 and 12 beingseparated by intervening sheets of electrically insulatingdielectricmaterial 13 and 14. The conductive foils 11 and 12 may comprise aluminumfoil or some other similar material and the sheets of dielectricmaterial l3 and 14 may comprise any known electrically insulatingdielectric which is capable of being fabricated in tape-like rolls. Forexample, the dielectric material may comprise paper of asuitable'thickness and dielectric strength suchas Kraft paper, linenpaper or the like, sheets of a low loss dielectric resin such as Mylar(polyethylene-terephthalate), polypropylene, or.

other suitable, known dielectric material. The sandwiched layers oftape-like conductive foils l1 and 12 and intervening layers ofelectrically insulating dielectric material 13 and 14 are rolledtogether to form the coil structure shown in FIG. 1. While only twoconductive foils 11 and 12 and suitable intervening layers aredescribed, it is believed obvious that additional foils and layers canbe provided should such a structure be desired or required in order toobtain desired operating characteristics.

If the coil structure 10 of FIG. 1 were unrolled and laid out flat, itwould appear schematically as shown in FIG. 2 where S, and 8, representthe start of the tapelike conductive foils 11 and 12, and F, and F,represent the'finish of each of the respective foils. When thusvisualized, the manner in which the structure obtains its capacitivereactance characteristic can be more easily appreciated. Also, it isbelieved obvious from a consideration of the wound, interleaved, turnsof the conductive foils l1 and 12 shown in FIG. 1 wherein the structureacquires its inductive reactance characteristics to thereby provide acombined capacitance-inductance reactance when employed in an electricalcircuit.

The inductance of the coil 10 can be greatly increased by providing amagnetically permeable core member 15 to the structure asshown in FIG.3. This can be accomplished by employing two E-shaped core membersfabricated from laminated, E-shaped, magnetically permeable steelmembers. The E-shaped core members are arrayed in a manner such that thecentral leg 16 extends through a central opening in the coil 10.Suitable connecting arms 19 secured to the outer legs 17 and 18 of theE-shaped core members hold the arrangement in assembled relation. Inputand output terminal means to various points on the conductive foils areshown at T,, T, and T, and are connected as described hereinafter.

In order for a cap-reactor such as shown in FIG. 3 of the drawing to beconnected in electrical circuit rela-' I tionship with a load, it mustbe specifically tailored or designed to serve that load. The particularembodiment of that invention described herein is specifically designedto serve as a starting and ballast circuit for a fluorescent lamp. Forthis purpose, the device must serve to supply a high voltage surgeacross the lamp terminals for starting purposes hence requiring that thedevice function as a step-up transformer to provide the higher than linevoltage surge for starting. Thereafter, the device must serve to limitcircuit current since a fluorescent lamp, while operating, exhibitsnegative resistance. The circuit also preferably should exhibit highpower factor characteristics. In existing fluorescent ballast circuitusing a conventional wire wound transformer and separate individuallyconnected capacitors, the circuit arrangement often appears as shown bythe equivalent circuit of FIG. 5. In this arrangement, the turns ratiobetween the secondary and the primary of the transformer supply providesthe required voltage step-up for starting while the serially connectedcapacitor assures the creation of the desired starting voltage surge andhigh power factor correction.

FIG. 4 of the drawing illustrates the manner in which a capreactor suchas shown in FIG. 3 may be physically connected to a source of supplypotential and across a fluorescent lamp load so that it operates inaccordance with the equivalent circuit shown in FIG. 5. In thearrangement shown in FIG. 4, both input leads T, and T, from a singlephase supply of alternating current, such asa conventional, 60 cycle,-120 volt-l5 amp residential power supply, are connected to differentpoints on the same conductive foil such as 11. The number of foil turnswhich are included between the points of connection of the terminals T,and T, in effect determines the effective inductance of the primarywinding of the transformer. The output from the transformer thuscomprised is obtained preferably by connecting the load 21, such as afluorescent lamp, across the second conductive foil 12 between thefinish point F, of the second conductive foil 12, which comprises thesecondary of the transformer, and a terminal T, which is connected tothe starting point S, of the first conductive foil 11. Since thestarting point S, of foil 1 l is at the same potential as the inputterminal T, and the output terminal T it will be seen that these twopoints are in fact at the same common potential and may be treated as asingle, common terminal point which may be grounded.

In FIG. 4, the transformer action of the portion of the conductive foil11 intermediate the terminal points T, and T acting as a step-upprimary, induces a steppedup voltage from end to end of each of thefoils 11 and 12, and which is taken off of foil 12 acting as a secondaryand applied across load 21 serially through the effective interturncapacitance. This serial capacitance is determined by the overall lengthof the conductive foils l1 and 12, the width of the conductive foils,the spacing between the foils, the nature of the dielectric insulatinglayers separating the foils and the operating frequency of the circuitas is described more fully in the above referenced Gray US. Pat. Number2,521,513. The inductance of the conductive foil 12 and serialcapacitance provides both inductance and capacitance in series with thefluorescent lamp load 21. As a consequence, the structure will operateto provide the desired current limiting, high inductive starting voltagesurges, and high power factor characteristic effects required for use asa fluorescent lamp starting and ballast circuit in the manner of theequivalent circuit shown in FIG. 5.

While in the particular embodiment of the invention disclosed a step-uptransformer connection has been described in detail, it is believedobvious to one skilled in the art that a step-down transformer functionreadily could be obtained to satisfy the requirements of a differentload by appropriate rearrangement of the points on the respectiveconductive foils l1 and 12 to which the input supply and output loadterminals are connected. Further, it is believed obvious that the tapoffpoints on the second conductive foil 12 could be placed at someintermediate points along the length of foil 12 to thereby adjust theturns ratio of the secondary to the primary winding of the transformer.

One of the problems heretofore encountered in the use of capreactors isthe desirability, and often the necessity, of using a liquid impregnatedcoil-capacitor system in order to obtain higher corona starting voltagesand better thermal properties than can be obtained with an unimpregnatedor solid-impregnated system. FIG.'6 of the drawings illustrates apreferred form of construction of the capreactor described hereinbeforein connection with FIGS. 1-5. In this preferred embodiment of theinvention, the cap-reactor structure of FIG. 3 (connected in the mannerillustrated in FIG. 4) is enclosed in a suitable liquid-tight, metalcase 25 which completely encloses the rolled coil-capacitor conductivefoils and intervening layers of electrical insulation together withmagnetically permeable core member. Suitable, liquid-tight, electricallyinsulated lead-in conductors are provided to allow for connection to thesupply and load terminals T T and T With the cap-reactor thus enclosedthe rolled conductive foils and intervening electrically insulatingdielectric layers may be liquid impregnated in a vacuum with a suitabledielectric liquid such as an askarel or other capacitor impregnant forimproving the starting voltage and thermal properties of the system. Byenclosing the entire core member, foil windings and insulating layers ina liquid-tight metal case that is outside most of the magnetic field ofthe structure, the metal case will not dissipate energy by acting as ashorted turn and at the same time will minimize magnetic couplingproblems and leaks around the leads to the structure.

Because. the metal case enclosing the liquid impregnated, woundconductive foils and core member might produce an audible hum, theliquid impregnated and metal encased cap-reactor is further enclosed ina second housing 27 which may be of metal, plastic, or other suitablehousing material having a traditional ballast shape. The space betweenmetal case 25 and the outer housing 27 preferably is filled with aballast potting compound 28 such as sand-loaded asphalt in order toprovide improved sound deadening and heat distribution characteristicsto the completed structure.

From the foregoing description it will be appreciated that the inventionprovides an improved, combined capacitor-inductor reactor structure thatexhibits capacitor connected transformer characteristics and which issuitable for use as a fluorescent lamp starting and ballast circuit. Byreason of the special design of the cap-reactor and its enclosure in asuitable liquidtight housing, the cap-reactor structure can be liquidimpregnated to provide improved starting and thermal properties alongwith improved sound deadening and heat distribution characteristics.

Having described one embodiment of an improved, combinedcapacitor-inductor reactor device having capacitor-connected transformercharacteristics constructed in accordance with the invention, it isbelieved obvious that other modifications and variations of theinvention are possible in the light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiment of the invention described which are within the full intendedscope of the invention as defined by the appended claims.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a combined constant current capacitor-reactor device of the typeincluding spaced apart tape-like conductive foils with interveninglayers of electrical insulation rolled together to form a combinedcapacitor inductor reactor, the improvement comprising:

a first conductive foil having a starting point and a finishing point;

a second conductive foil having an electrically isolated starting pointand a finishing point;

first input terminal means connected to said starting point of saidfirst conductive foil;

second input terminal means-connected to said first conductive foil at aconnection point between said starting point and said finishing point ofsaid first conductive foil; first output terminal means connected tosaid finishing point of said second conductive foil,said firstconductive foil and said second conductive foil forming a predeterminedcapacitance which ele'ctrically appears in series with said finishingpoint of said second conductive foil; and

second output terminal means connected to said starting point of saidfirst conductive foil.

2. A combined constant current capacitor-reactor device according toclaim 1 wherein the distance between said starting point and saidfinishingpoint on said second conductive foil is a greater distance thanthe distance between said starting point and said connection point ofsaid second input terminal means on said first conductive foil.

3. A combined constant current capacitor-reactor device according toclaim 2 including a constant current load device and further including amagnetically permeable core member, a portion of said core member beingsurrounded by the rolled turns of the tape-like conductive foils andintervening layers of electrical insulation to provide a high reactanceconstant current device for said constant current load device.

4. A combined constant current capacitor-reactor device according toclaim 3 wherein the rolled turns of conductive foils and interveninglayers of electrical insulation are liquid impregnated with a dielectricliquid and the entire structure including the magnetically permeablecore member is enclosed in a suitable liquid tight metal case providingelectrically insulated terminal connections to said first input terminalmeans, said second input terminal means, said first output terminalmeans, and said second output terminal means, and wherein the liquidimpregnated and metal encased capacitor-reactor structure is furtherenclosed in a second outer housing providing access to the insulatedterminal connections, and having a space intermediate the second outerhousing in the metal case filled with a suitable ballast compound, suchas sand-loaded asphalt for improved sound deadening and heatdistribution.

5. A combined constant current capacitor-reactor device according toclaim 4 wherein said first input terminal means and said second inputterminal means comprise primary input terminals for connection to asource of supply potentiaL and wherein said constant current load deviceis connected between said first output terminal means and said secondoutput terminal means.

6. A combined constant current capacitor-reactor device according toclaim 5 wherein said constant current load device is a fluorescent lampconnected

1. In a combined constant current capacitor-reactor device of the typeincluding spaced apart tape-like conductive foils with interveninglayers of electrical insulation rolled together to form a combinedcapacitor inductor reactor, the improvement comprising: a firstconductive foil having a starting point and a finishing point; a secondconductive foil having an electrically isolated starting point and afinishing point; first input terminal means connected to said startingpoint of said first conductive foil; second input terminal meansconnected to said first conductive foil at a connection point betweensaid starting point and said finishing point of said first conductivefoil; first output terminal means connected to said finishing point ofsaid second conductive foil, said first conductive foil and said secondconductive foil forming a predetermined capacitance which electricallyappears in series with said finishing point of said second conductivefoil; and second output terminal means connected to said starting pointof said first conductive foil.
 2. A combined constant currentcapacitor-reactor device according to claim 1 wherein the distancebetween said starting point and said finishing point on said secondconductive foil is a greater distance than the distance between saidstarting point and said connection point of said second input terminalmeans on said first conductive foil.
 3. A combined constant currentcapacitor-reactor device according to claim 2 including a constantcurrent load device and further including a magnetically permeable coremember, a portion of said core member being surrounded by the rolledturns of the tape-like conductive foiLs and intervening layers ofelectrical insulation to provide a high reactance constant currentdevice for said constant current load device.
 4. A combined constantcurrent capacitor-reactor device according to claim 3 wherein the rolledturns of conductive foils and intervening layers of electricalinsulation are liquid impregnated with a dielectric liquid and theentire structure including the magnetically permeable core member isenclosed in a suitable liquid tight metal case providing electricallyinsulated terminal connections to said first input terminal means, saidsecond input terminal means, said first output terminal means, and saidsecond output terminal means, and wherein the liquid impregnated andmetal encased capacitor-reactor structure is further enclosed in asecond outer housing providing access to the insulated terminalconnections, and having a space intermediate the second outer housing inthe metal case filled with a suitable ballast compound, such assand-loaded asphalt for improved sound deadening and heat distribution.5. A combined constant current capacitor-reactor device according toclaim 4 wherein said first input terminal means and said second inputterminal means comprise primary input terminals for connection to asource of supply potential, and wherein said constant current loaddevice is connected between said first output terminal means and saidsecond output terminal means.
 6. A combined constant currentcapacitor-reactor device according to claim 5 wherein said constantcurrent load device is a fluorescent lamp connected between said firstoutput terminal means and said second output terminal means.